The field of the present invention relates to chain-type trenching machines. In particular, apparatus and methods are described herein for digging wide trenches with a multiple-chain trenching machine.
A wide variety of construction situations require the digging of trenches in rock or other hard earth formations. Chain-type trenching machines are commonly used for this purpose, and several such machines, as well as other types of digging machines, are described in U.S. Pat. Nos.: 5,497,567; 5,471,771; 4,908,967; 4,432,584; 3,954,301; 3,050,295; 2,939,692; 2,926,896; and 2,650,812. Each of these nine patents is hereby incorporated by reference as if filly set forth herein.
It has been observed that while these trenching machines work fairly well for digging relatively narrow trenches (less than about 24 inches wide, for instance), such machines become increasingly inefficient for digging relatively wide trenches (greater than about 36 to 48 inches, for example). Such wide trenches are required to accommodate large buried structures, such as large diameter oil and gas pipelines, for example. In addition, placement of structures within the trench frequently requires that relatively finely divided material (such as sand, gravel, crushed rock, etc.) must be placed in the trench to provide a support bed (also referred to as padding or bedding material) for the structure. This requires an extra step after digging the trench and before placing the structure within the trench, and requires the transportation of the material to and placement within the trench.
It is therefore desirable to provide apparatus and methods for digging wide trenches in rock or other hard earth formations which are more efficient than those currently available. It is also desirable to provide apparatus and methods for digging such trenches in which relatively finely divided material is simultaneously produced and deposited within the trench to provide a support bed for a structure placed within the trench.
Certain aspects of the present invention may overcome one or more aforementioned drawbacks of the previous art and/or advance the state-of-the-art of trenching apparatus and methods, and in addition may meet one or more of the following objects:
To provide apparatus and methods for digging wide trenches in rock or other hard earth formations;
To provide apparatus and methods for digging wide trenches in rock or other hard earth formations using multiple endless-chain digging assemblies;
To provide apparatus and methods for digging wide trenches in rock or other hard earth formations using multiple endless-chain digging assemblies, wherein two or more relatively narrow secondary endless-chain digging assemblies are operated at a relatively fast speed for cutting relief slots;
To provide apparatus and methods for digging wide trenches in rock or other hard earth formations using multiple endless-chain digging assemblies, wherein a relatively wide primary endless-chain digging assembly is operated at a relatively slow speed in a forward direction between the secondary digging assemblies for disintegrating and removing material left between the relief slots;
To provide apparatus and methods for digging wide trenches in rock or other hard earth formations using multiple endless-chain digging assemblies, wherein secondary digging assemblies are operated in a reverse direction for depositing disintegrated material within the trench, the deposited material serving as a support bed for structures subsequently placed within the trench; and
To provide apparatus and methods for digging wide trenches in rock or other hard earth formations using multiple endless-chain digging assemblies, wherein two or more relatively narrow secondary endless-chain digging assemblies are operated at a relatively fast speed in a reverse direction for cutting relief slots and for depositing disintegrated material within the trench, the deposited material serving as a support bed for structures subsequently placed within the trench.
One or more of the foregoing objects may be achieved in the present invention by a multiple-chain trenching machine comprising a prime mover with a trenching head assembly operably connected thereto. The trenching head may be raised, lowered, and/or pivoted relative to the prime mover, and comprises: a) a frame having a proximal end operably connected to the prime mover, and a distal end; b) one or more pairs of primary sprockets, each pair comprising a proximal primary sprocket rotatably mounted on the frame and a distal primary sprocket rotatably mounted on the frame at the distal end thereof; c) a primary endless-chain digging assembly (hereinafter, xe2x80x9cprimary chainxe2x80x9d) engaged with and circulating around each pair of primary sprockets and comprising a plurality of pivotably connected links and a plurality of cutting tools substantially rigidly mounted thereon for disintegrating the earth formation; d) one or more pairs of secondary sprockets, each pair comprising a proximal secondary sprocket rotatably mounted on the frame and a distal secondary sprocket rotatably mounted on the frame at the distal end thereof; e) a secondary endless-chain digging assembly (hereinafter, xe2x80x9csecondary chainxe2x80x9d) engaged with and circulating around each pair of secondary sprockets and comprising a plurality of pivotably connected links and a plurality of cutting tools substantially rigidly mounted thereon for disintegrating the earth formation.
The primary chains are substantially wider than the secondary chains, and the diameters and positions of the sprockets may be such that each of the secondary chains cuts more deeply into the ground formation than the primary chains, thereby producing a narrow relief slot corresponding to each secondary chain. The primary chains are driven in a forward chain direction, so that disintegrated material is removed from the trench by the motion of the primary chains. The secondary chains may be driven in a forward or a reverse chain direction at about one to eight times the linear speed of the primary chains. If operated in the reverse chain direction, the disintegrated material produced by the secondary chains may be deposited within the trench by the motion of the secondary chains. The material thus deposited may serve as a support bed for whatever structure is to be subsequently placed within the trench.
One or more of the foregoing objects may be achieved in the present invention by a method for digging wide trenches in rock or other hard earth formations using multiple endless-chain digging assemblies, comprising the steps of: a) positioning a trenching head assembly (as described in the previous paragraph) in the ground formation at the desired depth; b) driving the primary chains in a forward direction; c) driving the secondary chains at about one to eight times the linear speed of the primary chains; d) moving the trenching head assembly in a forward trench-digging direction; e) conveying, by the forward motion of the primary chains, disintegrated material out of the trench; and f) if the secondary chains are driven in the reverse direction, depositing, by the reverse motion of the secondary chains, disintegrated material within the trench to serve as a support bed for a structure subsequently placed therein.
Additional objects and advantages of the present invention may become apparent upon referring to the preferred and alternative embodiments of the present invention as illustrated in the drawings and described in the following written description and/or claims.